Re: gEDA-user: X-Y placement files

[Dan McMahill <dan@mcmahill.net>]

On Mon, Mar 15, 2004 at 09:40:49PM -0800, Matt Ettus wrote:
> 
> 
> Is PCB capable of creating X-Y placement files for pick and place?  The format
> seems pretty simple.
> 
> Thanks,
> Matt
> 

Hi Matt,

I have mostly implemented this.  Do you have any good data from a
manufacturer on the exact format they like to see?  It is fairly
industry standard?

What I'm doing is having the routine calculate the centroid of the
pins/pads on the fly so you're not sensitive to where the mark may
be on the footprint.  The only thing I have left to do is rotation.
Any suggestions on the algorithm?  Any idea what the standard definition
might be?  For example, if I have an 8 pin DIP or SOIC, what is the
angle of this:

1  8
2  7
3  6
4  5

Is that 0 degrees or +90 degrees?

DJ has suggested an approach that looks which quadrant pin #1 is in
after you find the centroid and then using a definition like:

pin #1 quadrant, rotation

1, +180 degrees
2, +90 degrees
3, 0 degrees
4, -90 (or should this be written as +270) degrees

Any thoughts based on real experience as to cases where this will fail?

I suppose (thinking while typing) if pin 1 falls on an axis, I need to
properly deal (SIP packages, 2 pin packages, etc) and a 1 pin part 
would always be 0 and a 1 pad part could be 0 or 90 based on aspect
ratio of the pad.

Comments?  Suggestions?

-Dan

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